Like I said, I use both. Sometimes there's no rhyme or reason why I choose one over the other. Whatever happens to be handy for trout. I do like 6X flouro for dry flies, and very difficult situations. 6X won't drag a small fly under as long as it's a good presentation. I flip flop for streamers and wets on trout. Whatever happens to be easiest to grab. For other fish that pull hard, I use mostly heavy flouro. I will not hesitate to use mono too, but I have so much flouro, it's what I use and have confidence in. It's extremely rare for me to break a fish off on either line. When breaking off snags, both are very strong.
I mostly use the same knots for mono and flouro. Again, for trout it's basically the same knots. Improved clinch, Davy, or Lefty's Loop. Triple surgeon's for leaders. For my heavy line and conventional fishing, no improved clinch, or Davy. I'll add in a Palomar(a knot I don't care for but easy to tie), and a no name knot, very similar to a San Diego Jam.
No name knot.
This knot has proven to be very strong, and impact resistant. It is bulky, and uses a lot of line to tie, but I trust it as much as the Lefty Loop. I cannot remember if I have ever broken off a lure at the knot. If so, I know it was on a snag, and never a fish. Ugly, bulky, wasteful, and STRONG.
briansII